Actuator with stroke end locking means and stroke adjusting means



Oct. 10, 1961 R. c. BODEM ETAL ACTUATOR WITH STROKE END LOCKING MEANSAND STROKE ADJUSTING MEANS 2 Sheets-Sheet 1 Filed June 23, 1958INVENTORS. Ray 6. Bodem. Howard M. Geyer.

Their Attorney.

Oct. 10, 1961 Filed June 25, 1958 R. c. BODEM ETAL ACTUATOR WITH STROKEEND LOCKING MEANS AND STROKE ADJUSTING MEANS 2 Sheets-Sheet 2 INVENTORS.Ray C. Bodem. Howard M. Geyer.

Th'eir Attorney.

United States This invention pertains to fluid pressure operatedactuators, and particularly to a linear actuator having stroke endlocking means and means for adjusting the stroke of the actuator.

In order to use the same actuator in different installations, it isnecessary to incorporate means for adjusting the stroke of the actuatorwithout varying the physical dimensions of the actuator cylinder. Inaddition, in some installations it is only necessary to lock theactuator against movement in one position, for instance, at one end ofthe stroke. Moreover, where fluid pressure operated actuators aresubjected to high ambient temperatures, it is necessary to provide meansfor circulating fluid through the actuator chambers to preventcongealing thereof and to cool the actuator. The present inventionrelates to a linear actuator including releasable means for locking theactuator piston against movement at one stroke end position thereof;externally adjustable means for varying the stroke of the actuator; andmeans permitting the circulation of fluid in metered quantities toprevent congealing thereof due to high ambient temperatures.Accordingly, among our objects are the provision of a fluid pressureactuator including stroke end locking means; the further provision of afluid pressure operated actuator including stroke end locking means andmeans for automatically releasing the locking means upon application ofpressure fluid so as to effect actuator movement away from the strokeend locking position; the further provision of fluid pressure operatedactuator including means for adjusting the stroke of the actuatorpiston; and the still further provision of an actuator of the aforesaidtype including means for circulating fluid through the actuator chambersto effect cooling thereof.

The aforementioned and other objects are accomplished in the presentinvention by incorporating fingertype locking means in an actuator incombination with an adjustable drain tube, the position of whichdetermines the stroke of the actuator piston. Specifically, the unitcomprises a cylinder having a reciprocable piston therein capable offluid pressure actuation in both directions. The piston divides thecylinder into an extend chamber and a retract chamber, and includes anintegral rod which extends outside of the cylinder for attachment to amovable load device. The cylinder is adapted to be connected to a fixedsupport.

In order to facilitate circulation of fluid through the retract chamber,a pressure drop bushing is incorporated in therod end of the cylinder,and the piston rod is slideably supported by the pressure drop bushingand extends therethrough. The pressure drop bushing functions in themanner set forth in copending application Serial No. 648,361 filed March25, 1957, now Patent No. 2,953,119, inthe name of Howard M. Geyer andassigned to the assignee of this invention, such that whenever there isa pressure differential across the pressure drop bushing, a meteredamount of fluid will flow between the pressure drop bushing and thepiston rod to a drain conduit. A second pressure drop bushing issubjected to the pressure existent in the extend chamber for permittingthe circulation of cooling fluid therethrough to a drain tube.

The drain tube is coaxially disposed within the cylinder and extendsinto the hollow piston rod. The drain tube has a closed inner end havinga plurality of radial pasatent 'ice sages therethrough adjacent the endthereof, which pas sages communicate with an annular groove in a bushingfixedly attached to the tube. The bushing has a plurality of radialports therein which are normally closed by the piston rod or the pistonhead. By adjusting the position of the drain tube relative to thecylinder, the ports in the bushing will be uncovered during extendingmovement of the piston, and when the ports are uncovered the extendchamber will be connected to drain thereby limiting the stroke of theactuator piston and determining the extend stroke end position of thepiston.

The piston also carries a pair of pivotally mounted locking fingers orjaws which are engageable with a fixed locking cam attached to the headend of the cylinder. When the actuator piston is moved to the fullyretracted stroke end position, the locking fingers engage the lockingcam and a spring biased piston, and thereby prevent extending movementof the actuator piston under the influence of the load device attachedthereto. In order to release the stroke end locking means upon theapplication of pressure fluid to the extend chamber, the spring biasedpiston is moved out of engagement with the locking fingers whereby thelocking means are disengaged so as to permit extending movement of theactuator piston.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings, wherein a preferred embodiment of the present invention isclearly shown.

in the drawings:

FIGURE 1 is a fragmentary longitudinal sectional view of an actuatorconstructed according to this invention with the stroke end lockingmeans engaged.

FIGURE 2 is a fragmentary longitudinal sectional view of the actuatorwith the stroke end locking means disengaged depicting the stroke of thepiston as limited by the adjustable drain tube.

FIGURE 3 is a fragmentary sectional View depicting the limits ofadjustment of the drain tube for varying the stroke of the actuator.

FIGURE 4 is an enlarged sectional view taken along line -4-4 of FIGURE2.

With particular reference to FIGURE 1, the actuator includes a cylinder10 having a head end cap 12 attached thereto by means of a nut 14. Areciprocable piston 16 having an integral hollow rod 18 with a closedouter end is disposed within the cylinder 10. The piston 16 divides thecylinder into an extend chamber 20 and a retract chamber 22. The bore ofthe cylinder 10 adjacent the head end thereof is slightly larger asindicated by numeral 24, than the bore of the cylinder traversed by thepiston 16, and the enlarged bore 24 is formed with a shoulder 26.

The hollow piston rod 18. extends through the rod end of the cylinder 10and slideably engages a pressure drop bushing 28. The pressure dropbushing is formed with an external annular groove 30 and a plurality ofaxial passages 32 which connect the groove 30 with the retract chamber22. The cylinder 10 is formed with a retract port 34 that communicateswith the annular groove 30. The inner diameter of the pressure dropbushing is spaced slightly from the outer periphery of the piston rod 18so as to form an annular orifice whereby a metered amount of fluid willflow from the retract chamber 22 to an annular groove 36 formed betweenthe rod end of the cylinder and the piston rod 18 due to a pressuredifferential across the bushing 23. The annular groove 36 is connectedto a drain conduit 38. A plurality of low pressure metallic sealingrings 40 are retained in sealing engagement with the piston rod 18 andthe rod end of the cylinder by a nut 42 which threadedly engages thecylinder 10. The retract stroke end position of the piston 16 relativeto the cylinder 10 is determined by engagement between the nut 42 and anut 44 which threadedly engages the piston rod 18 and abuts the nut 42as shown in FIGURE 1 when the actuator is fully retracted.

The piston 16, as seen particularly in FIGURES l and 4, has a pair ofdiametrically opposed arcuate fingers, or jaws, 46 pivotally attachedthereto by means of pins 48. The fingers 46 are formed with curved ends50 having beveled, or tapered, inner surfaces 52. The fingers 46 areengageable with a fixed cam member 54 having a complementary frustoconical surface 56 engageable with the surfaces of the fingers. The cam54 is fixedly attached to the head end cap 12 by means of a nut 58. Thecam 54 also has a second frusto conical surface portion 59 whichintersects the surface 56.

'In order to maintain the fingers 46 in locking engagement with the cam54, an auxiliary reciproc-able sleeve piston 69 is disposed within theenlarged portion adjacent the head end of the cylinder 16. The piston 66is normally urged into engagement with the shoulder 26 by a compressionspring 62, one end of which engages the head end cap 12 and the otherend of which engages the piston 60. The piston 60 is formed with afrusto conical surface 64 and a cylindrical surface portion 66. When theactuator piston 16 is in the fully retracted stroke end position asshown in FIG- URE l, the cylindrical portion 66 of the piston engagesthe outer peripher of the fingers 46 so as to preclude disengagingmovement the locking fingers 46 from the cam 54 due to an external loadacting on the piston rod 18.

The piston 66 carries a pressure drop bushing 68 which slidably engagesa cylindrical portion 70 of the cam 54. The slight annular clearancebetween the pressure drop bushing 68 and the cylindrical periphery 70 0fthe cam 54 constitutes an orifice permitting a metered flow of fluidfrom the extend chamber 20 to the space 72 to the left of the piston 60as seen in FIGURE 1. The space '72 is connected by one or more passages74 in the cam member 54 to the hollow interior thereof. The cylinder 16is formed with an extend port 76 which communicates with the extendchamber 20. In addition, the cylinder has a trunnion 78 attachedthereto, as seen in FIGURE 4, by which means the cylinder can beattached to a fixed support.

In order to release the stroke end lockingmeans, fluid under pressure isapplied to the extend chamber 20 through the port 76 while the retractchamber 22 is connected to drain through port 34. This pressure fluidwill act on the piston 60 and effect movement of the piston 60 to theleft thereby compressing the spring 62. When the piston 60 has beenmoved to the left throughout a sufficient distance so that thecylindrical periphery 66 thereof is disengaged from the locking fingers46, the pressure fluid acting on the piston 16 will effect movement ofthe piston 16 to the right, as viewed in FIGURE 1. Thus, the piston 69constitutes means for releasing the stroke end locking means, since assoon as the cylindrical periphery portion 66 of the piston 69 isdisengaged from the fingers 46, relative movement between the coactinginclined surfaces 52 and 56 will result in outward pivotal movement ofthe fingers 46 so as to disengage the fingers 46 from the cam 54.

Assuming the actuator piston to be in an extended position, as shown inFIGURE 2, upon application of pressure fluid to the retract chamber 22while the extend chamber 20 is connected to drain, the piston I6 willmove to the left, as viewed in FIGURE 2. As the piston 16 approaches theretract stroke end limit p0- sition the curved ends of the fingers willride up the frusto conical portion 59 of the cam and engage the frustoconical portion 64 of the piston 60 so as to move the piston 69 to theleft, as viewed in FIGURE 1. As soon as the locking fingers move out ofengagement with the frusto conical portion 59 and into engagement withthe frusto conical portion 56, the spring 62 will move the piston 66 tothe position of FIGURE 1 there by locking the actuator piston in thefully retracted stroke end position.

The cam 54 is also formed with an internally threaded portion '79. Adrain tube 89 having a closed inner end and an open outer end iscoaxially disposed within the cylinder Lid and extends into the hollowpiston rod 18. The tube St has a plurality of circumferentially spacedradial ports 82 formed therein adjacent the closed inner end thereof andsupports a bushing 84 having an internal annular groove 86 and aplurality of circumferentially spaced radial ports 88. The closed outerend of the tube St) is tapered, as indicated by numeral 90 and threadedat 92, and the bushing 84 is securely held in fixed relation relative tothe tube 8%) by a nut 94. The open end of the tube is connected todrain, and in addition the tube is formed with a plurality ofcircumferentially spaced radial ports 96 that communicate with anannular groove 98 formed between the cam 54 and the outer periphery ofthe tube 30.

The tube 80 is formed with axially spaced threaded portions 1% and 162,the threads 1410 engaging the threads 79 on the cam 54, and the threads1432 receiving a out 184 having a sealing edge 106 that engages the endof the cam 54 and the outer periphery of the tube St The drain tube 80is longitudinally adjustable relative to the cylinder 10 for determiningthe extend stroke end limit position of the piston 16. Normally, theextend stroke end limit position of an actuator piston is determined byengagement of the piston with the rod end of the cylinder. However, inthe instant actuator, the extend stroke end limit position can be variedby adjusting the longitudinal position of the drain tube 80 relative tothe cylinder 1 3. Thus, as seen in FIGURE 2 when the piston 16 is movedto the right throughout a predetermined distance, the ports 88 in thebushing 84 will be uncovered by the piston. When the ports 83 in thebushing are uncovered, the extend chamber 20 is connected to drainthrough the ports 88, the groove 86, the ports 82 and the drain tube 80.Accordingly, further movement of the piston 16 to the right under theurge of fluid pressure cannot be effected, and thus the extend strokeend limit position of the actuator is determined by the position of thedrain tube 80.

With reference to FIGURE 3, in order to adjust the longitudinal positionof the drain tube 80 relative to the cylinder 10, the nut 104 isloosened, whereupon the drain tube 80 can be rotated relative to the cam54 so as to adjust the longitudinal position thereof relative to thecylinder 10. The limits of adjustment of the tube 80 relative to thecylinder 10 are shown in full and dotted lines in FIGURE 3, and theselimits are determined by the length of the annular groove 98 between thecam 54 and the tube 80, since in order to maintain the circulation ofcooling fluid through the extend chamber, the ports 96 in the tube mustalways communicate with the annular groove 98. After the drain tube 80has been adjusted relative to the cylinder, the nut 104 is tightened tomaintain the drain in the adjusted position.

When the extend chamber 20 is subjected to fluid under pressure, theorifice means constituted by the slight annular clearance between thepressure drop bushing 68 and the cam 54 will permit a metered amount offluid to flow from the extend chamber 20 to the space 72. This fluidwill flow through the passage 74 to the groove 98, and from the groove98 through ports 96 to the drain tube 86. Likewise, when retract chamberis subjected to fluid under pressure, a metered amount of fluid willcirculate through the orifice means between the pressure drop bushing 28and the piston rod 18 through an annular groove 36 and the drain tube38. Accordingly, when either actuator chamber is subjected to fluidunder pressure, the fluid will be maintained in a state of continuouscirculation by reason of the pressure drop bushings and the drain tubes.

While the embodiment of the invention has herein disclosed constitutes apreferred form, it is to be understood that other forms might beadopted.

What is claimed is as follows:

1. A fluid pressure operated actuator assembly including, a cylinder, areciprocable piston disposed in said cylinder capable of fluid pressureactuation in both directions, said piston having a hollow rod with aclosed outer end extending outside of said cylinder and dividing saidcylinder into an extend chamber and a retract chamber, a pressure dropbushing disposed between the rod end wall of said cylinder and the outerperiphery of said piston rod, the inner surface of said pressure dropbush ing being radially spaced from the outer periphery of said rod soas to form an orifice through which a metered amount of fluid can flowdue to a pressure differential across said bushing, a drain conduitconnected with the low pressure side of said pressure drop bushing, adrain tube assembly coaxi'ally disposed within said cylinder and havinga closed inner end disposed within said piston rod, port means in saiddrain tube assembly adjacent the closed inner end thereof cooperatingwith said piston so as to be uncovered and thus connect the extendchamber to drain for determining the extend stroke end limit position ofsaid piston, means for adjusting the position of said drain 6 tubeassembly relative to said cylinder to vary the extend stroke end limitposition, and means constituting an orifice connecting the extendchamber to said drain tube assembly whereby a metered amount of fluidcan flow from said extend chamber to drain due to a pressuredifferential across said last recited orifice.

2. The fluid pressure operated actuator assembly set forth in claim 1wherein said last recited means comprises a second pressure drop bushinglocated adjacent the head end of said cylinder, and means connecting thelow pressure side of said second pressure drop bushing with the interiorof said drain tube assembly.

References Cited in the file of this patent UNITED STATES PATENTS1,834,773 Fellmann et a1. Dec. 1, 1931 2,333,274 Schannell Nov. 2, 19432,478,790 Stephens Aug. 9, 1949 2,494,752 Gambell Jan. 17, 19502,547,029 Loungway Apr. 3, 1951 2,634,709 Fageol Apr. 14, 1953 2,685,275Caldwell Aug. 3, 1954 2,771,060 Allbright Nov. 20, 1956 2,787,254Rhoades Apr. 2, 1957 2,851,995 Westcott Sept. 16, 1958 FOREIGN PATENTS551,207 Germany Oct. 21, 1930

